Alibaba Cloud DNS Intelligent Resolution (Line Segmentation) Causes Slow Access Troubleshooting for Users in Some Regions
In the network optimization of enterprise websites and applications,
Alibaba Cloud resolves intelligent DNS resolution (route segmentation)
is a critical function. By accurately scheduling access requests from different operators (such as China Telecom, China Unicom, China Mobile, and Education Network) or different provinces/regions (such as North China, South China, and overseas) to the nearest server IP address, access latency can be greatly reduced.
However, in the actual operation and maintenance and SEO site investigation, this "counter-intuitive" phenomenon often occurs:
Clearly, the intelligent analysis subdivision line has been opened, and the access speed of users in some regions or under specific networks has slowed down, and even the problems of web page jam and loading failure have occurred.
As an SEO website optimizer, you not only need to pay attention to the website content and external links, but also need to ensure that the technical bottom layer of the website (DNS resolution and CDN/server response speed) is stable as a rock. This article will deeply analyze the core reasons for slow access in some areas due to intelligent analysis line segmentation, and provide a set of troubleshooting and optimization solutions that can be directly implemented.
1. why do some areas slow down after intelligent analysis and segmentation?
The core logic of intelligent parsing is:
"Return the corresponding server IP according to the source IP"
. However, the domain name resolution process does not occur directly between the "user computer" and "Aliyun authoritative DNS", and there is also a key role in the middle--
LocalDNS (local recursive DNS, such as operator default DNS, 114.114.114.114, or 8.8.8.8)
.
When the line subdivision is too complex or the configuration is improper, it is easy to have problems in the following links:
1. LocalDNS scheduling drift (most common cause)
If the user has set up a public DNS (such as 8.8.8.8 or some public DNS), or the geographical location/operator of the local operator's LocalDNS exit IP is not consistent with the user's actual network:
ECS protocol is not enabled: If the LocalDNS does not support or does not enable the EDNS Client Subnet (ECS) protocol, Alibaba Cloud authoritative DNS can only obtain the egress IP address of the LocalDNS, not the real IP address of the user.
Misjudged line: Alibaba Cloud authoritative DNS will treat this LocalDNS as a visitor. If a user of Guangdong Telecom uses a public DNS located in Beijing, DNS may judge the user as a "Beijing line" or even a "default line", thus returning to the server IP in Beijing, resulting in long-distance access across provinces/operators and soaring delay.
2. Lack of "default (Default)" line bottom
Some operation and maintenance personnel in the configuration of the line, only set up "Telecom", "Unicom", "Mobile" three sub-lines, or for specific provinces (such as "Guangdong Telecom", "Zhejiang Mobile").
Set the line,
No "default" line added
.
Blind Zone Falling: When a niche operator in a remote area (such as Radio and Television, Great Wall Broadband, Education Network or Overseas IP) initiates an access, the authoritative DNS may not be able to return the correct IP or trigger an abnormal response due to the failure to hit any subdivision line, resulting in connection timeout or redirection delay.
3. Line priority conflict and IP library identification deviation.
The line matching of Alibaba Cloud DNS resolution follows certain priority rules (for example:
User-defined lines> Carrier subdivision lines> Regional lines> All-network default lines
).
If overlapping route rules are configured (for example, both "East China Region" and "Jiangsu Province" are configured), and the IP address performance of the associated servers is different, the resolution may result in the failure to match the expected node.
In addition, the IP address segment of the network operator is occasionally changed or borrowed. If there is a lag in parsing the IP library update, the occasional "misjudgment of IP attribution" will also cause some nodes to slow down.
4. Advanced Analysis Service Downgraded Due to Account Arrears
In Alibaba Cloud DNS resolution, more accurate route segmentation (such as segmentation into provinces, cities, and global countries and regions), faster global TTL refresh, and high-frequency health checks often rely on
Alibaba Cloud DNS Enterprise Edition or Premium Edition
Wait for the paid package.
If the enterprise fails to pay attention to the financial status in time during the operation and maintenance process, resulting in insufficient account balance, the paid version of the analysis service may be automatically downgraded to the free version or the basic version due to arrears.
After the downgrade, the originally configured fine lines and high-frequency scheduling functions may fail or revert to the default coarse-grained lines, causing confusion in parsing and scheduling in many parts of the country. Therefore, in the daily operation and maintenance process, regular recharge of Alibaba Cloud accounts to maintain sufficient account funds is an important infrastructure link to ensure that advanced DNS intelligent scheduling and high availability services are not interrupted.
2. Five-Step Troubleshooting Method: Accurately Locate the Root Cause of Slow Access
When you receive a notification that the user feedback website in a certain area is very slow, you can follow the following steps to diagnose:
[Step 1] Collect network information of affected users (IP, LocalDNS, province/operator)
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[Step 2] Use dig/nslookup to verify authoritative DNS and LocalDNS resolution results
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[Step 3] Check the cloud resolution console: confirm whether there is a "default line" and priority conflict
│
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[Step 4] Catch a packet or query to verify whether the LocalDNS supports and carries ECS fields
│
▼
[Step 5] Test MTR Link and Server Real Response Delay in Combination with National Dial Test Tools
Step 1: Collect the affected user's base
Basic Network Information
Instead of blindly modifying the console configuration, first collect three key pieces of information from the user who is responding to the problem (or through the front-end buried point):
The current public IP address of the user. You can access cip.cc or ip.sb on the terminal.
The LocalDNS of the user's computer configuration (for example, through ipconfig /all under Windows).
The actual slow access URL and the specific phenomenon (DNS resolution takes a long time, or TCP connection is slow).
Step 2: Compare the analysis results of authoritative DNS and LocalDNS
On the local terminal or test server, use
dig
command to query the authoritative Alibaba Cloud DNS and the LocalDNS used by the user:
Bash
#1. Directly query Alibaba Cloud authoritative DNS (replace with your domain name and Alibaba Cloud DNS address, such as ns1.alidns.com)
dig @ ns1.alidns.com www.yourdomain.com subnet = User public IP/32
#2. Simulate the user's LocalDNS query
LocalDNS IP of user dig @ www.yourdomain.com
Comparative analysis: Observe whether the IP addresses returned by the two queries are consistent. If the IP obtained by directly checking the authoritative DNS is correct, but the IP found by LocalDNS is wrong/cross-operator, it indicates that the problem lies in the LocalDNS cache or scheduling drift caused by not supporting ECS protocol. If the authoritative DNS is directly checked and the wrong IP is returned, it indicates that there is overlap or logical error in the route division rules of the console.
Step 3: Check the line configuration of the cloud resolution console
Log in to the Alibaba Cloud DNS console, go to the Domain Name Resolution Settings page, and check the following three points:
Default Line Existed: There must be one record with the Resolve Request Source set to Default. This is a "guaranteed haven" for all missed subdivision line requests ".
Whether there is an error in parsing record coverage: check whether the IP of the "telecom" line is incorrectly filled with the IP of the "Unicom" computer room.
Check TTL time setting: If the line rule has been modified recently and TTL is set for a long time (e.g. 86400 seconds/24 hours), the LocalDNS refresh progress varies across the country, resulting in some areas still accessing the old IP.
Step 4: Verify ECS (EDNS Client Subnet) Compatibility
If certain special public DNS is commonly used by users in the affected area, resulting in incorrect scheduling:
Use the dig subnet tool to test whether Alibaba Cloud authoritative DNS can correctly identify the client IP with the mask.
If it is determined that the LocalDNS has stripped the ECS information, causing Alibaba Cloud to be unable to identify the real source, it is usually necessary to add global node support in the area, or consider cooperating with HTTPDNS technologies to bypass the scheduling defects of traditional DNS.
Step 5: Use the national multi-node dial test tool to confirm the link
With the help of third-party dial test platforms (such as Boece and ITDOG), initiate DNS and Ping test for affected provinces and operator nodes:
Observe the resolution response time of different nodes and the returned IP address.
If the dial test shows that the resolved IP is correct, but the ping delay is extremely high or the packet loss is serious, it indicates that the problem is not DNS resolution, but the network backbone link from the operator in the region to the target server room is congested, or the server firewall is limiting traffic.
3. targeted optimization and solutions
After the cause is identified, the following combination strategies can be used to repair and optimize:
Cause of the failure
Recommended solution
Applicable Scenarios
Missing default line
Add an A/CNAME record of "parsing request source: default" and point to a general CDN or two-line node.
All intelligent parsing scenarios (required)
LocalDNS scheduling drift
The mobile terminal/App introduces HTTPDNS to directly obtain accurate IP through HTTP interface
App, applet, game client
Subdivision lines are too complex
Tighten segmentation granularity: prioritize by region/large operator, reduce too fragmented provincial lines
Small and medium-sized sites with limited node resources
Delinquency leads to downgrade of paid version
Recharge your Alibaba Cloud account in a timely manner to ensure that Enterprise DNS and intelligent scheduling are not interrupted.
Large and medium-sized enterprises using advanced intelligent parsing
Cache refresh slow
Temporarily reduce TTL (e. g. 60 seconds to 300 seconds), and then increase it after the line adjustment is stable.
During frequent line adjustments/migrations
1. Specification of "default line subdivision line" combined architecture
The most robust parsing configuration architecture should follow the "pyramid" pattern:
At the bottom of the tower (covering the bottom): set the default line of the whole network and point to the host or CDN fusion node with the best network compatibility and sufficient bandwidth.
Tazhong (large category): for the three major mainstream operators (telecommunications, Unicom, mobile) configuration of independent lines.
Tip (fine): Fine lines are set up only for specific provinces with clear edge node deployment (e. g. Guangdong Telecom, Beijing Unicom).
2. Introduce HTTPDNS to solve the mobile scheduling problem
For Web App or Native App services, traditional LocalDNS scheduling is naturally tampered with, does not include ECS protocol, cache is not available, etc.
Defect. By integrating Alibaba Cloud HTTPDNS, clients directly send HTTP/HTTPS requests to HTTPDNS servers to obtain IP addresses, which can completely solve the problem of slow access caused by operator LocalDNS scheduling drift.
3. Operation and maintenance logistics and service support: prevent analysis exceptions caused by arrears
DNS belongs to the infrastructure of infrastructure, once the resolution degradation or failure, the impact on website traffic and SEO collection is devastating.
In actual project management, many enterprises' cloud resolution DNS paid versions (such as exclusive version and exclusive version), CDN belt deduction fees and high-security IP are deducted monthly/by volume. In order to avoid the demotion of DNS intelligent resolution to the free version due to the expiration of funds (resulting in the failure of subdivision lines and the shutdown of custom lines), the operation and maintenance team should have a financial early warning mechanism.
Ensure that the enterprise public cloud account has sufficient capital reserves and arrange special personnel to follow up
Alibaba Cloud account top-up
The renewal is a precondition for ensuring the continuous and stable operation of cloud resolution DNS intelligent lines, high anti-DDoS and CDN nodes.
DNS Optimization Suggestions from the Perspective of 4. SEO
From the perspective of search engine optimization (SEO), DNS resolution delay is directly related to spider crawling efficiency and web page first screen loading speed (TTFB performance in Core Web Vitals):
Reduce crawling latency: The IP addresses of search engine spiders (such as Baiduspider and Googlebot) are usually assigned to specific BGP data centers. Ensure that intelligent resolution returns the node with the fastest response as a "spider route" or "default route", which helps to increase the crawl frequency of spiders.
Avoid parsing dead loops and empty returns: Any DNS query failure caused by unmatched lines will be judged by the search engine as unstable and the site weight will be reduced.
Maintain a reasonable TTL balance: When the line changes frequently, reduce the TTL first; After the line is stable, it is recommended to set the TTL to 300 seconds to 600 seconds, which can not only reduce the LocalDNS query pressure, but also ensure the scheduling efficiency.
Summary
The line segmentation function of Alibaba Cloud DNS is a "double-edged sword". If you use it well, you can achieve extreme nearby access. If you configure it improperly or ignore the LocalDNS complex network environment, it may cause the problem of slow access in some areas.
The core logic for troubleshooting such issues is:
Clarify the mapping relationship between "real user IP-LocalDNS IP-Aliyun authoritative DNS"
. By completing the default bottom line, repairing the scheduling drift, combining MTR link testing, and completing it regularly.
Alibaba Cloud account top-up
Ensure that the enterprise-level advanced analysis service is not interrupted, in order to ensure that the entire network users can obtain high-speed, stable access experience.
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